In 17 patients (eleven males, six females) with Morquio-Brailsford syndrome (mucopolysaccharidosis IV) we have used onlay femoral and tibial autografts placed posteriorly and secured to the laminae of C1 and C2 to obtain satisfactory occipito-C1/C2 posterior fusion. They were immobilised postoperatively in a halo-plaster body jacket for four months. The age at operation varied between three and 28 years. Those with myelopathic symptoms of recent onset made some recovery, but severely myelopathic patients showed little or no recovery. We advise prophylactic occipitocervical fusion in these patients since the cartilaginous dens is not strong enough to ensure atlanto-axial mechanical stability